Lookup Transformation vs Join

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Lookup Transformation vs Join

Post  AK on Fri Jul 10, 2015 3:16 am

Hi ,

Just a bit introduction about me . I am SQL developer , also part of the [SSIS]ETL process too but not an expert level. At present i am part of one of the DataWarehouse project , While populating fact we need to join with dimensional table to populate some of the dimensional attributes . This job can be done well with lookup transformation , but another way we can use by joining dimensional table in OLEDB Source in dataflow task.
Please comment on the approach if we are joining dimension table in OLEDB Source .?
Will there any performance improvement by joining this way?
Why lookup transformation for , any advantage ?

AK

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Re: Lookup Transformation vs Join

Post  sharvan.kumar.83@gmail.co on Fri Aug 07, 2015 2:08 pm

Lookup is good for small table like value and description Key value pair. But when there are many attribute associated with data then it make more sense to go for dimesion table and use that as a joining.

Any way in fact you should always keep the surrogate key of dimension table.


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Re: Lookup Transformation vs Join

Post  ngalemmo on Fri Aug 07, 2015 8:11 pm

Most ETL tools will cache lookups in memory, so they tend to be much faster than joining as a source. In particular, when you are loading facts.
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